I would really apreciate a Linux client and would be willing to pay for it, too.
I currently use wine (PlayonLinux) to run GW2 on my PC and the performance is very low (and my system is on the higher-end: i7-3770K; AsRock MB; Radeon HD7990). I get about 40 fps at medium detail…
If A-Net thinks it’s to expensive to port to Linux, I would suggest to start a crowdfunding campaign (indiegogo/Kickstarter) and let the community pay for it.
Maybe it would be a good idea to contact the wine devs for help and tipps on porting (and i think they might have rough ideas on the effort required).